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A team of researchers has discovered a protein in semen can affect a woman's brain, prompting ovulation.

The research, led by Gregg Adams of the University of Saskatchewan, says male mammals have accessory sex glands that contribute seminal fluid to semen. But the researchers noted the role of the fluid and the glands was not well known.

"From the results of our research, we now know that these glands produce large amounts of a protein that has a direct effect on the female," Adams said in a release about the study.

For this study, the researchers looked at llamas and cattle. Llamas are induced ovulators, meaning the animals ovulate only when they have been inseminated. Cows — and humans — are spontaneous ovulators, meaning a regular buildup of hormones stimulates the release of an egg.

The protein has been dubbed the ovulation-inducing factor. It acts as a hormonal signal and triggers the release of other hormones in a woman, sending a signal to the ovaries to release an egg, the researchers found.

The research appears in this week's edition of the journal Proceedings of the National Academy of Sciences.

"The idea that a substance in mammalian semen has a direct effect on the female brain is a new one," Adams said. "This latest finding broadens our understanding of the mechanisms that regulate ovulation and raises some intriguing questions about fertility."